Performance of oxidation resistant coatings for C/C composites as aircraft brakes

Abstract

A modified phosphate coating on C/C composites used for aircraft brakes was made from zinc chloride,phosphoric acid,zinc phosphate and aluminum phosphate. In order to study the properties of the modified coating,an unmodified phosphate coating and a ceramic coating,which principally consists of silicon and boron,were also investigated. Results showed that all three coatings had excellent oxidation resistance at 500 ℃ for 100 h and the maximum mass loss is 1.25%. The mass loss of the C/C composite with a modified phosphate coating was 1.76% when the composite was subjected to oxidation at 700 ℃ for 30 h in air,and the value was 1.98% when the composite was subjected to thermal shock in air for 30 cycles (from 900 ℃ for 3 min to at room temperature for 2 min) followed by shock in air for 10 cycles (from 1 100 ℃ for 3 min to room temperature for 2 min). The performance of the modified phosphate coating is the best among the three coatings. It has excellent oxidation resistance and thermal shock resistance.